Generally, representative large-scale display apparatuses include Liquid Crystal Displays (LCDs), Plasma display Panels (PDPs), etc.
Unlike self-emission type PDPs, LCDs essentially need a separate backlight unit due to absence of self light emitting devices.
Backlight units for use in LCDs are classified into edge type backlight units and vertical type backlight units according to positions of light sources. In an edge type backlight unit, light sources are disposed at left and right edges or upper and lower edges of an LCD panel and a light guide plate is disposed to uniformly distribute light throughout a surface of the LCD panel, which ensures uniform luminance and enables production of an extremely thin display panel.
A vertical type backlight unit is normally applied to displays of 20 inches or more. The vertical type backlight unit advantageously has greater light efficiency than the edge type backlight unit owing to a plurality of light sources being disposed below a panel and thus, is mainly used in a large-scale display requiring high luminance.
Conventional edge type or vertical type backlight units have adopted Cold Cathode Fluorescent Lamps (CCFL) as a light source.
The backlight units using CCFLs, however, have several disadvantages, such as consumption of a great quantity of power because power should always be applied to a CCFL, low color reproduction efficiency of about 70% that of a Cathode Ray Tube (CRT), and environmental pollution due to use of mercury.
Currently, backlight units using Light Emitting Diodes (LEDs) are being studied as a solution to the above described problems.
In the case of backlight units using LEDs, turning on or off a part of an LED array is possible, which can achieve remarkable reduction in power consumption. In particular, RGB LEDs exhibit color reproduction beyond 100% of a color reproduction range proposed by the National Television System Committee (NTSC) and can provide more vivid images to consumers.